Dental restorative materials are known for restoring the function, morphology and integrity of dental structures damaged by physical damage or caries-related decay of enamel and/or dentin. Dental restorative materials are required to have high biocompatibility, good mechanical properties and mechanical and chemical resistance over a long period of time given the harsh conditions for a restorative material in the buccal cavity.
Dental restorative materials include glass ionomer cements having good biocompatibility and good adhesion to the dental hard tissues. Moreover, glass ionomer cements may provide cariostatic properties through the release of fluoride ions. Glass ionomer cements are cured by an acid-base reaction between a reactive glass powder and a polyalkenoic acid. However, conventional glass ionomer cements have a relatively low flexural strength and are brittle due to salt-like structures between the polyacid and the basic glass.
The mechanical properties of glass ionomer cements may be improved by the selection of the polyacidic polymer. For example, a polymer having polymerizable moieties as pendant groups can be crosslinked in order to increase the mechanical resistance of the resulting glass ionomer cement.
Japanese Patent Publication No. 2005-65902A discloses a dental adhesive composition comprising, as a polymerizable monomer containing a particular carboxylic acid, a carboxylic acid compound having a (meth)acryloyl group and a carboxyl group which are bound to an aromatic group. However, such a polymerizable monomer having an ester group quickly degrades in an acidic medium.
Chen et al. and Nesterova et al. (Chen et al., J. Appl. Polym. Sci., 109 (2008) 2802-2807; Nesterova et al., Russian Journal of Applied Chemistry, 82 (2009) 618-621) disclose copolymers of N-vinylformamide with acrylic acid and/or methacrylic acid, respectively. However, none of these documents mentions the introduction of a further polymerizable moiety into the copolymer.
WO2003/011232 discloses water-based medical and dental glass ionomer cements that can be post-polymerized after the cement reaction. The dental glass ionomer cements consist of two separate polymers, wherein one of the polymers has a pendant post-polymerizable moiety linked to the polymer through an ester bond. However, this ester bond between the polymer and the polymerizable moieties is again prone to hydrolytic cleavage in acidic media. Moreover, crosslinking of the glass ionomer may lead to the shrinkage of the dental composition in particular when the molecular weight of the crosslinking polymer is low.
WO2012/084206 A1 discloses a polymer for a dental glass ionomer cement. However, WO2012/084206 does not disclose a specific combination of components for a composition of a dental glass ionomer cement.